JPH07180828A - Heat-generation process and plant simultaneously functioningas regeneration of adsorbent and fertilizer production - Google Patents

Abstract

PURPOSE: To reduce the use of absorbent and to improve the quality of fertilizer by providing with a heating unit having a desulfurizing zone, a dust-collecting unit, a gas-liquid contactor, a recovering means for used absorbent and filtering means for recovered absorbent. CONSTITUTION: Combustion exhaust gas containing sulfur and nitrogen is desulfurized and denitrified by a heating unit 1 and fume containing no calcic absorbent is sent to a chimney through the dust-collecting unit. Ammonium solution and gas containing CO2 are fed into a gas-liquid contactor 9. Ammonium solution is filtered through the contactor 9 and the concentration of ammonium carbonate is increased. The condensed carbon ammonium is extracted at the bottom of the contactor 9. The recovery of used absorbent is done by reactor 17-1, 17-b. Ammonium sulfate solution and solution containing residue calcium carbonate are sent to a filter 22 and the ammonium sulfate solution containing almost no calcium carbonate particles flows out from the filter 22. With this, the use of calcic absorbent can be saved and the quality of the fertilizer is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the field of heat generators including means for treating combustion fumes. In a heat generator using a fuel containing a large amount of sulfur or nitrogen, a large amount of sulfur oxides, nitrogen oxides, and unburned combustible compounds are discharged by combustion, which causes a pollution problem.

Regulations on such exhaust gas are becoming more and more stringent, and fuels having a high sulfur content are almost unusable.

Various techniques have been proposed to solve this problem.

According to French patent FR-2,609,150, it is possible to reduce the production of sulfur oxides, in particular sulfurous acid gas, emitted by heating elements which can use fuels with a high sulfur content.
To that end, the three main components are combined to form a miniature assembly. That is, preferably a cold wall combustion chamber, a waste heat recovery boiler for recovering sensible heat of combustion gas, an intermediate for desulfurization of gas passing between an upstream furnace and a downstream exchanger without a significant internal exchange surface. It is a circulating bed.

An improved desulfurization effect of this plant is proposed in French Patent FR-2,636,720.

In the latter type of heater, a calcareous pulverulent adsorbent is injected in the form of a suspension or a dry powder in order to trap sulfur oxides. This step is performed at about 1000 ° C.

A major problem in such boilers relates to the production of large quantities of spent adsorbents, primarily quicklime and anhydrous calcium sulfate, which are becoming increasingly difficult, expensive, and unpopular with the public.

A known method to solve this problem is to use an adsorbent called regenerable dolomitic adsorbent, as disclosed in French patent FR-2,671,855, which is the final The emission of solid solid substances is very low, while the fumes can be treated very well.

According to this prior art, the sulfur is released in the form of concentrated SO2 and H2S by regenerating the spent adsorbent. Collect these chemicals in the storage hopper,
Then, for example, the Claus plant is loaded in order to convert sulfur into its elemental form. However, these "post-treatments" proved to be expensive and were not something that users in need of such technology would be willing to use.

[0010]

SUMMARY OF THE INVENTION The present invention proposes a new method of treating the combustion fumes of a heating element. Since the used adsorbent is regenerated, the amount of final emission can be reduced and the amount of adsorbent used can be reduced.

Moreover, since the adsorbent used is not a bitter ash type but a calcareous type, and lime or natural limestone itself is inexpensive, the present invention is not so expensive to implement.

Furthermore, the present invention improves the quality of the sulfur trapped in the fumes and improves the quality of the fertilizer. This is because the sulfur-containing substance obtained in the regeneration process itself is a fertilizer, and depending on the fertilizer, it may be added as its composition.

This improvement in quality associated with the present invention makes it advantageous for its use.

Moreover, this new technique, which is the object of the present application, is close to the concept of "zero solid waste". So the concept is, as it is easy to understand, to improve the quality of combustion products in order to use them cheaply.

The above object can be achieved by the present invention.
The object of the present invention comprises in particular a heating element having a desulfurization zone, a dust removal means, a chimney for discharging the exhaust gas emitted from the dust removal means, a regeneration means for the spent adsorbent, and a filtration means for the regenerated adsorbent. It is a heat generation plant.

According to the invention, the adsorbent used is calcareous, the plant may further comprise means for preparing the solution used for regeneration, and the sulfur-containing material leaving the filtration means may be fertilizer.

More precisely, the solution preparation means may be constituted by an exchanger, and the ammonia solution supplied from the storage means is brought into contact with a part of the gas discharged from the dust removal means, and the solution is stored in the storage means. Add the stored carbon dioxide. The solution prepared is a concentrated ammonium carbonate solution.

The heat exchanger may be operated with the contactor.

The heating device is preferably provided with a combustion chamber, a desulfurization and / or denitrification chamber and a convection exchanger, and the desulfurization chamber is provided with supply lines for regenerated adsorbent, non-regenerated adsorbent and ammonium hydroxide.

Further, the adsorbent regeneration means may be composed of a concentrated ammonium carbonate solution and at least one reactor to which a part of the spent calcareous adsorbent discharged from the dust separator is sent. The reactor is provided with a means for stirring the mixed solution and preferably a heat recovery means.

The present invention also particularly relates to a process comprising the following steps. -Combustion in the heat generator-Desulfurization and denitrification of the exhaust gas from the combustion in the heat generator-Heat exchange of the treated exhaust gas-Dust removal of the treated exhaust gas-Recovering the adsorbent, Part of it is recirculated to the desulfurization / denitrification zone, and the rest is supplied to the regeneration zone.-Fume from which dust is removed is released into the atmosphere.-Adsorbent is regenerated. Recirculate-Discharge fumes from the regeneration stage

According to the invention, the exothermic process further comprises: -Use a calcareous adsorbent- (i) Prepare an ammonium carbonate solution with ammonium hydroxide and carbon dioxide before the regeneration step-Calcium adsorption to be regenerated with the solution in at least one reactor during the regeneration step Mixing with the agent-filtering the mixture obtained by the regeneration-recovering the regenerated calcareous adsorbent before recycling it to the desulfurization / denitrification zone, while also recovering the ammonium sulphate solution

The carbon dioxide used in (i) has the advantage that it can be obtained from the fumes leaving the heating element and / or from a specific container.

As another feature, the process may be configured to perform heat exchange simultaneously with the preparation of the ammonium carbonate solution and / or regeneration of the adsorbent.

The regeneration is preferably carried out continuously using several reactors.

Calcium carbonate and / or carbon dioxide may additionally be fed to the various reactors.

The final filtration step may be carried out with a vigorous backflow of water.

After recovery of the regenerated adsorbent, it may be further processed before recycling.

When the regenerated adsorbent is used in a dried form, it is dried as an additional treatment.

When used in the form of a suspension, a step of adjusting the water content and / or adding a stabilizer is additionally performed.

Other features and advantages of the present invention will be apparent from the following non-limiting description of embodiments and the accompanying drawings.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some of the basic elements of this plant are known to those skilled in the art and will not be described in detail here. Included in the following description only in connection with their specific purpose and / or other elements.

The plant shown in the figure includes a heat generator 1.
The heating element is divided into three elements. That is, the combustion chamber 1-having a heating device (not shown) in the gas flow direction
a, intermediate desulfurization and denitrification chamber 1-b and convection heat exchange zone 1-
c. In the desulfurization and denitrification chamber 1-b, ammonium hydroxide from the storage container 4 is passed through the line 2, the non-regenerated adsorbent recirculated through the line 3-a, and the line 3-b.
The regenerated adsorbent is supplied through. The combustion exhaust gas is discharged from the heat generator 1 through the line 5 and flows to the dust removing device 6. The fumes without adsorbent are then sent to the chimney 7 via the transfer line 8.

The plant of the present invention further comprises a gas-liquid contactor 9, such as a packed column. In this contactor 9,
Ammonia solution is supplied from the storage container 4 to the upper part thereof through the line 10 and CO2 is supplied to the lower part thereof through the line 11.
A containing gas is supplied. What is drawn into the main fume pipe 8 is supplied to the line 11 through the branch circuit 12,
It is also preferably supplied from a line 13 connected to a CO2 generator or a CO2 storage container 14.

The ammonia solution is filtered through the contactor 9, and the ammonium carbonate concentration increases as it proceeds. The concentrated ammonium carbonate solution is extracted through line 15 at the bottom of contactor 9.

The contactor 9 comprises several parts 9-a, 9-b ...
Divided into, between which the solution is extracted and cooled by the heat exchanger 16.

Regeneration of the adsorbent is carried out in the reactors 17-a, 17-b ... Which are arranged in series. A stirring and mixing means 18 is provided in these reactors. It is preferred to provide some of the reactors, especially the first device, with a heat extraction means 19 consisting of a bundle of tubes immersed in the liquid phase.

Spent adsorbent is fed through line 20 to at least one of the reactors 17-a (texture) and ammonium carbonate solution is passed through line 21-a to the first reactor 17-a. is supplied to a.

In order to accelerate the conversion of the anhydride to ammonium sulfate, the ammonium carbonate is supplied to the next reactor 17-b or the like through a line 21-b or the like. The solution containing ammonium sulphate and residual calcium carbonate is sent through line 23 to filter 22.

The ammonium sulfate solution containing almost no calcium carbonate particles is passed through the line 24 to the filter 2
It flows out from 2. This liquor may be further sent to a decomposer (not shown) to further reduce the calcium carbonate balance and charged to an evaporator / granulator (not shown) tailored to the desired particle size of the final product.

The calcium carbonate is sent from the filter 22 to the line 25 in the form of mud, and the water content is adjusted by supplying water via the line 26. By this final water supply, storage and flow rate control are possible, and transportation by line 3-b and reinjection of regenerated adsorbent into desulfurization / denitrification chamber 1-b can also be performed under optimal conditions. .

In order to further understand the purpose of the present application, the preferred procedure of implementation in the above plant is described below.

In summary, the process of the present invention comprises a step of desulfurizing and denitrifying fumes in the heat generator 1, which step is carried out in the tubeless zone 1-b or another internal zone provided for that purpose. preferable. Regenerated adsorbents are especially used to recover sulfur oxides, and concentrated ammonium hydroxide solutions are sprayed into the combustion fumes to reduce nitrogen oxides. This has the advantage that an ammonium hydroxide storage facility for denitrifying fumes is already in place.

The final dust removal process is also performed at the outlet of the heat generator 1, where most of the adsorbent is recovered. This dust removal is performed by means 6 such as an electrostatic precipitator known to those skilled in the art.

At the outlet of the dust separator 6, a part of the used adsorbent is not particularly treated, and the heat generator 1 is directly fed through the line 3-a.
Be recycled. This is to increase the desulfurization efficiency of the fumes and the adsorbent usage rate (that is, the adsorbent sulfation rate). The remaining used adsorbent is recycled to the regeneration unit 1 via line 20.
Sent to 7.

The first step of the regeneration process consists of preparing an ammonium carbonate solution according to the following reaction mechanism. 2NH4OH + CO2 (NH4) 2CO3 + H2O

Ammonium hydroxide for denitrifying fumes may be used in this preparation, or other ammonia or ammonium hydroxide may be used. The carbon dioxide supply source may be fumes discharged from the regeneration device (original mama). The line 12 allows such an extraction to take place at the outlet of the dust separator 6. These fumes are converted to CO2 by a known gas separation means 14 such as a membrane or a high CO2 gas generator.
The content may be increased.

Since heat is generated by the preparation, it is preferable that this step further includes heat exchange with the outside. This allows the temperature to be low enough, typically 40 ° C to 80 ° C
It is kept for a short time, and the reaction can be completed in the shortest possible time. The heat exchanger 16 is provided for that purpose.

The regeneration step itself, in which the used adsorbent is brought into contact with the ammonium carbonate solution, is carried out by the following reaction mechanism. CaSO4 + (NH4) 2CO3 CaCO3 + (NH4) 2SO4

The spent adsorbent contains a significant amount, sometimes 30% to 70%, of quicklime, and is not made of pure anhydrous. It may be charged directly into reactor 17-a, or it may be first slaked with water and / or steam to convert quicklime to slaked lime. At this regeneration stage, exchange with the outside is performed once or several times to adjust the medium temperature. The heat exchange is carried out by supplying or extracting energy depending on the nature of the adsorbent (in particular, its sulfation rate) and whether or not the adsorbent has been preliminarily digested. This heat exchange is performed by means 19.

The regeneration is preferably carried out in a series of reactors 17-a, 17-b ... Instead of a single reactor in order to convert the anhydride to ammonium sulfate as completely as possible.

When the stirring means 18 is provided in each of the reactors 17-a, 17-b ..., Mixing can be performed efficiently.

In addition, ammonium carbonate, carbon dioxide solution or other compounds can be added at several points in the series of reactors to accelerate the reaction.

Finished the regeneration process (via line 23)
The mixture is then passed through a filter 22 to recover calcium carbonate and slaked lime. This filtration step is performed, for example, by backflowing water to suppress the residual ammonium sulfate concentration of the adsorbent that is re-injected into the desulfurization and denitrification chamber 1-b of the heat generator through the line 25 and then the line 3b.

The regenerated adsorbent is preferably further processed before reuse in the heating element 1. For example, when it is used in a dried form, it is a drying process, and when it is used in the form of a suspension, the water content of the medium is adjusted, and a stabilizer for the suspension is added.

Line 26 in the drawing is a water supply line.

Finally, the high-concentration ammonium sulfate solution that has undergone the filtration step is sent to a known solidifying means through a line 24, and the obtained solid may be used alone as a fertilizer, or a fertilizer having a more complicated composition may be used. You may use it as an ingredient.

By obtaining such a solution, the present invention has very economic advantages. In fact, according to known mechanisms, the regeneration of the spent adsorbent results in sulfur enriched SO
Emitted in the form of 2 and H2S, these chemicals must be fed to specific equipment (such as the Claus plant) to convert sulfur to elements.

The highly concentrated ammonium sulphate solution finally obtained according to the invention makes it possible to improve the quality of the fertilizer and thus avoid the conventional saturation of sulfur channels.

Of course, those skilled in the art can make various improvements and additions to the above plant and process without departing from the scope of the present invention.

The process described here is suitable for a carried bed heater with a fine particle size adsorbent, since the regeneration according to the invention gives a powdery adsorbent with a good desulfurization effect. However, it can also be applied to other in situ desulfurization techniques such as dense or circulating fluidized bed furnaces.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of a plant according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C01C 1/10 A 6908-3K F23J 15/00 J

Claims (14)

[Claims] 1. A desulfurization / denitrification zone (1) utilizing an adsorbent.
a heat generator (1) having -b), means (6) for removing dust from combustion fumes, a chimney for discharging exhaust gas from the means (6), and means (17) for regenerating used adsorbent
And a means (22) for filtering the regenerated adsorbent, the adsorbent used is a calcareous substance, the sulfur-containing substance emitted from the filtration means (22) is a fertilizer, and the plant is further regenerated. Means (9) for preparing a solution for the purpose of contacting the ammonia solution supplied by the storage means (4) with a part of the gas emitted from the dust removing means (6), and bringing the solution into the solution (14). A heat-generating plant, characterized in that it comprises an exchanger (9) adapted to add the carbon dioxide stored therein and the solution thus prepared by said means (9) is a concentrated ammonium carbonate solution. 2. Plant according to claim 1, characterized in that it further comprises a heat exchanger (16) operating in cooperation with said means (9). 3. The heat generator includes a combustion chamber (1-a), a desulfurization and / or denitrification chamber (1-b) and a convection exchanger (1-c), the chamber (1-b) being regenerated and adsorbed. 3. A supply line (2,3-a, 3-b) for delivering the agent, the non-regenerated adsorbent and the ammonium hydroxide supplied by the storage means (4). Plant. 4. The adsorbent regeneration means is at least one reactor (17) to which the concentrated ammonium carbonate solution and a part of the spent calcareous adsorbent discharged from the dust separator (6) are supplied.
-a), wherein the reactor is provided with means (18) for stirring the mixture.
4. The plant according to any one of 3 to 3. 5. Plant according to claim 4, characterized in that at least one of the reactors further comprises a heat recovery means (19). 6. Combustion in a heat generator-Desulfurization and denitrification of exhaust gas from combustion in the heat generator-Heat exchange of treated exhaust gas-Dust removal of treated exhaust gas- Collect the adsorbent, recirculate a part of it to the desulfurization / denitrification zone, and supply the rest to the regeneration zone.- Release dust-removed fumes into the atmosphere-Regenerate adsorbent-Regenerated adsorbent Recycle to desulfurization / denitrification zone-in an exothermic process consisting of discharging fumes from the regeneration stage, the process-using a calcareous adsorbent- (i) prior to the regeneration process ammonium hydroxide and , Part of the fumes of the heat generator (1) and / or concentrated ammonium carbonate solution with carbon dioxide from a specific container
Prepare-mix the solution with the calcareous adsorbent to be regenerated in at least one reactor during the regeneration process-filter the mixture obtained in the regeneration process-desulfurize / desulfurize the regenerated calcareous adsorbent Before recirculating to the nitrification zone, the adsorbent is recovered (line 25) while
An exothermic process comprising a step of recovering also ammonium sulfate solution (line 24). 7. Process according to claim 6, characterized in that the heat exchange is carried out simultaneously with the preparation of the ammonium carbonate solution and / or the regeneration of the adsorbent. 8. Process according to claim 7, characterized in that the preparation is carried out at a temperature between 40 ° C. and 80 ° C. 9. Reactor having several reactors (17-a, 1)
7-b ...) are carried out consecutively, the process according to any one of claims 6 to 8. 10. Process according to claim 9, characterized in that the supply of calcium carbonate and / or carbon dioxide is additionally carried out in different reactors. 11. Process according to any of claims 6 to 10, characterized in that the filtering step is carried out by backflowing water. 12. The process according to any one of claims 6 to 11, wherein the regenerated adsorbent is further treated after recovery before being recycled. 13. The process according to claim 12, wherein the additional treatment is drying. 14. Process according to claim 12, characterized in that the additional treatment is regulation of water content and / or additional supply of stabilizer.